Clozapine has been called an "atypical neuroleptic" because it does not induce the characteristic elevations in prolactin levels nor does it produce the extrapyramidal reactions common to "classical" neuroleptics. We are conducting a blinded crossover study comparing clinical and biological response of treatment refractory schizophrenics to clozapine as compared to haloperidol. When enough patients have been studied we will have clinical, neuropsychological, and SPECT studies of each patient on haloperidol, placebo and clozapine. These results may shed some light on the underlying mechanisms for the often unique clinical responsiveness of patients to clozapine. To date six patients have completed the protocol, an insufficient number to permit data analysis. One patient had a grand mal seizure. This person was noted to have developed a lot of fast activity on her electroencephalogram (EEG) at a low dose of the drug. We are obtaining serial EEG's to see if seizure risk can be predicted.